Anisotropy processing in low angle wells
AssigneeSchlumberger Technology Corporation
InventorJian Yang
Life of this patent
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Abstract
A method for logging subsurface formations penetrated by a wellbore include measuring electromagnetic properties of the formations using electromagnetic fields having a magnetic dipole axis parallel to a logging tool axis Electromagnetic properties of the formations are also measured using electromagnetic fields having a magnetic dipole axis oblique to the logging tool axis. A horizontal resistivity of the formations is determined from the parallel dipole axis measurements. A vertical resistivity, formation layer boundaries and a dip angle of the formations are determined from the oblique dipole axis measurements.
Claims19
A method for logging subsurface formations penetrated by a wellbore comprising:
- measuring electromagnetic properties of the formations using electromagnetic fields having a magnetic dipole axis parallel to a logging tool axis;
- measuring electromagnetic properties of the formations using electromagnetic fields having a magnetic dipole axis oblique to the logging tool axis;
- mapping a measured phase shift and attenuations to the properties of the formations with dipole approximations to convert non-dipole antenna measurements into an equivalent dipole antenna response;
- determining a horizontal resistivity of the formations from the parallel dipole axis measurements using a layered structure formation model;
- and
- determining a vertical resistivity, formation layer boundaries and a dip angle of the formations from the oblique dipole axis measurements.
A method for determining horizontal resistivity, vertical resistivity and formation dip of subsurface formations from electromagnetic measurements of subsurface formations, comprising:
- accepting as input to a computer measurements of electromagnetic properties of the subsurface formations made using electromagnetic dipole measurements having magnetic dipole axis substantially parallel to a well logging tool axis;
- accepting as input to the computer measurements of electromagnetic properties of the subsurface formations made using electromagnetic dipole measurements having magnetic dipole axis oblique to the well logging tool axis;
- mapping a measured phase shift and attenuations to the properties of the formations with dipole approximations to convert non-dipole antenna measurements into an equivalent dipole antenna response;
- in the computer, determining a horizontal resistivity from the parallel dipole axis measurements using a layered structure model;
- and
- in the computer, determining a vertical resistivity and formation dip angle from the oblique dipole axis measurements.
Dependencies are inferred from the claim text.